1. Field of the Invention
The present invention relates to a displacement sensor that detects displacement of a displacement body by detecting inductance change of a displacement detector coil that is caused by the displacement of the displacement body.
2. Description of the Related Art
A displacement detecting apparatus has been known which includes a displacement detector coil and a displacement body, and which is designed so that the displacement body is freely displaced relative to the displacement detector coil so as to cause a magnetic change of this displacement detector coil, as disclosed in Japanese Unexamined Patent Application Publication No. 05-040002. This displacement detecting apparatus generates an oscillator signal with a frequency corresponding to an inductance of the displacement detector coil, and outputs an output signal corresponding to a cycle of the oscillator signal, thereby detecting the displacement of the displacement detector coil as the inductance change of the displacement detector coil.
In this displacement detecting apparatus, the cycle of the oscillator signal is expressed by 2π(LC)1/2, and therefore the output signal contains a square root component of the product of an inductance (L) component and a capacitance (C) component. According to this displacement detecting apparatus, even when the displacement of the displacement body and the inductance change of the displacement detector coil have a linear relationship, the output signal changes nonlinearly relative to the displacement of the displacement body, which makes it inconvenient to use the output signal.
The present invention has been made to solve this problem, and an object thereof is to provide a displacement sensor that has improved the linearity of the output signal relative to the displacement of the displacement body.